We correlated two group size measures and the proportion of isolated males during spring, with total size of a french Alpine ibex (Capra ibex ibex) population. Mean group size (TM), typical group size (TGT) and the proportion of isolated individuals were highly correlated with the Belledonne-7 Laux population size (with respectively 83%, 74% and 86% of the variability of these measures explained by population size variations). The link between TM or TGT and population size was logarithmic. This shows a threshold beyond which group size increased only slightly. Proportion of isolated individuals decreased exponentially with population size. When using group size as a biological indicator, one has to be aware of not inducing confounding factors: in the case of species with sexual segregation outside the rutting period, we have to use observations made on one sex only. In this study, contrary to population size, ecological constraints such as food availability, social group composition and habitat structure seemed to have only little influence on group size.